Pen



FIG. 1 is a perspective view of a pen showing my new design;

FIG. 2 is the top plan view;

FIG. 3 is a front elevational view;

FIG. 4 is a right side elevational view; the left side being a mirror image thereof;

FIG. 5 is a rear elevational view; and,

FIG. 6 is a bottom plan view thereof. 

The ornamental design for a pen, as shown and described. 